: This competing-continuation application of a K05 Senior Scientist Award requests salary support for the PI to accomplish five goals. The first goal is to complete a program of research on how substance use, abuse, and disorder develop during adolescence. A biopsychosocial model that posits biological, sociocultural, parenting, peer, school, and cognitive-emotional factors that cumulate, interact, and transact across development guides this research. Hypotheses will be tested in an ongoing prospective study of 585 boys and girls who have been followed since age 4 and will turn 18 during the current year. Findings to date indicate that risk for early-onset substance use is enhanced by family history, adversity, and academic-social-conduct problems, whereas risk for adolescence-onset substance use derives especially from peer influences. The second goal is to complete a program of research on the prevention of substance use and related problem behaviors in adolescence. Based on the model and findings reported above, the PI has developed and implemented Fast Track, which is a comprehensive program for high-risk children (partially funded by NIDA). After screening over 9,000 kindergarteners, 891 were selected as high-risk and then randomly assigned to intervention or control groups. The intervention lasts 10 years and includes parent training, academic tutoring, social-cognitive skills training, peer coaching, mentoring, and vocational orientation. Findings after six years indicate that assignment to intervention leads to significantly less self-reported substance use (especially in girls), fewer associations with drug using peers, reduced aggressive behavior, fewer special education placements, and fewer psychiatric hospitalizations. Participants turn 14-16 years old this year and will be followed for the next five years. The third goal is to complete a program of public policy and services research on the costs, benefits, and utilization of health services, special education, and juvenile-justice system involvement by high-risk children. An economic study of Fast Track will be completed, along with analyses of the prediction of service utilization across time. The fourth goal is to enhance the PI?s research career development, particularly his ability to integrate basic developmental science with prevention program design and public policy analysis. He will become more learned in economic analysis and in the state of knowledge regarding adolescent substance use policy. The fifth goal is to enhance the PI?s ability to train new research scholars in a developmental approach to prevention and public policy toward adolescent substance use.